Extensive research on the chemotherapy of cancers has heretofore been conducted, with the chemotherapy of cancers commenced in the latter half of the 1940's for the control of nucleic acid metabolism. As antimetabolites to nucleic acids, 6-mercaptopurine was synthesized first, followed by the discovery of 5-fluorouracil.
5-fluorouracil was synthesized by Duschinsky in 1957 and found to have anti-cancer activity by Heidelberger et al. The compound has a wide anti-cancer spectrum range, produces outstanding effects especially on adenocarcinomas and is therefore one of the anti-cancer agents which are most widely used for clinical purposes. Since 5-fluorouracil is typical of antagonists to nucleic acid metabolism, intensive research is still continued on compounds having 5-fluorouracil as the basic skeleton.